vwait(n)              Tcl Built-In Commands              vwait(n)



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NAME
     vwait - Process events until a variable is written

SYNOPSIS
     vwait ?_v_a_r_N_a_m_e?
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DESCRIPTION
     This command enters the Tcl event loop  to  process  events,
     blocking the application if no events are ready.  It contin-
     ues processing events until  some  event  handler  sets  the
     value  of  variable _v_a_r_N_a_m_e.  Once _v_a_r_N_a_m_e has been set, the
     vwait command will return as soon as the event handler  that
     modified _v_a_r_N_a_m_e completes.

     In some cases the vwait command may not  return  immediately
     after  _v_a_r_N_a_m_e is set.  This can happen if the event handler
     that sets _v_a_r_N_a_m_e does not complete immediately.  For  exam-
     ple,  if an event handler sets _v_a_r_N_a_m_e and then itself calls
     vwait to wait for a different  variable,  then  it  may  not
     return  for  a  long  time.   During this time the top-level
     vwait is blocked waiting for the event handler to  complete,
     so it cannot return either.


KEYWORDS
     event, variable, wait

























Tcl                     Last change: 7.5                        1